From DE 103 48 960 A1, a transmission unit is known for distributing a drive torque from a transmission input shaft between two transmission output shafts, the transmission comprising at least two, at least three-shaft planetary gearsets. One respective shaft of one planetary gearset is connected with the transmission input shaft. In addition, one respective shaft of one planetary gearset constitutes one of the transmission output shafts and, respectively, at least one other shaft of each planetary gearset is in active connection with a shaft of the other planetary gearset. An operating-condition-dependent torque from one shaft of a planetary gearset can be supported via the active connection, depending on an operating condition of the respective other shaft of the other planetary gearset in active connection with it, in such manner that if a rotation speed difference occurs between the transmission output shafts, a torque that changes rotation speed difference is applied to the planetary gearset via the said active connection.
In addition, in the area of the active connection between the mutually connected shafts of the planetary gearsets an electric machine is provided, whose torque, produced in motor or generator operating mode, can be transmitted to the shafts of the planetary gearsets in such manner that a drive torque from a drive engine of a drive train of an all-wheel drive vehicle applied to the transmission can be distributed, according to need and in relation to the operating situation, in the vehicle's longitudinal direction between two vehicle axles or in the area of one vehicle axis in the direction transverse to the vehicle between two wheels, with a variable degree of distribution. In addition, the known transmission unit allows the possibility, in a front-wheel drive or rear-wheel drive vehicle, of distributing a drive torque from a drive engine in the area of a vehicle axis in the transverse vehicle direction between the wheels of the vehicle axis, with a variable degree of distribution.
The use of the transmission unit described above and known from the prior art in vehicles comprising a generator to charge the vehicle's batteries, leads to an increase in the total weight of the vehicle and in its manufacturing costs because of the incorporation of two electric machines in the vehicle, by comparison with vehicles respectively made with conventional distributor transmission without a variable degree of distribution.
Accordingly, the purpose of the present invention is to provide an all-wheel drive vehicle whose vehicle weight is lower compared with vehicles known from the prior art and which, besides, can be manufactured more cheaply.